#include "entry.h"

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

typedef enum parse_state {ID, DISTRIBUTION} parse_state;

entry entry_read(FILE *in, int max_id, int battlefields)
{
  entry result;

  if (in == NULL)
    {
      result.id = NULL;
      result.distribution = NULL;
      return result;
    }

  result.distribution = malloc(sizeof(int) * battlefields);
  result.id = malloc(sizeof(char) * (max_id + 1));

  if (result.distribution == NULL || result.id == NULL)
    {
      // allocation error; abort
      free(result.distribution);
      result.distribution = NULL;
      free(result.id);
      result.id = NULL;
    }
  else
    {
      // initialize FSM to read entry
      int ch;
      parse_state state = ID; // part of entry we're in (ID or DISTRIBUTION)
      int id_len = 0; // chars in id read so far
      result.id[0] = '\0'; 
      int curr_bf = 0; // number of battlefields read so far
      int curr_int = 0; // value of digits in number of units read so far
      while ((ch = fgetc(in)) != EOF && ch != '\n' && ch != '\r')
	{
	  switch (state)
	    {
	    case ID:
	      if (ch == ',')
		{
		  // start reading distribution of units
		  state = DISTRIBUTION;
		}
	      else if (id_len < max_id)
		{
		  // save character up to max (ignore characters beyond max)
		  result.id[id_len] = ch;
		  id_len++;
		  result.id[id_len] = '\0';
		}
	      break;
	      
	    case DISTRIBUTION:
	      if (ch == ',')
		{
		  // comma -- start reading next battlefield
		  curr_bf++;
		  if (curr_bf >= battlefields)
		    {
		      // too many battlefields
		      entry_destroy(&result);
		      return result;
		    }

		  curr_int = 0;
		}
	      else if (!isdigit(ch))
		{
		  // non-comma in integer distribution
		  entry_destroy(&result);
		  return result;
		}
	      else
		{
		  // update value of integer we're currently reading
		  curr_int = curr_int * 10 + (ch - '0');
		  result.distribution[curr_bf] = curr_int;
		}
	      break;
	    }
	}

      // eat carriage-return before line-feed in case some DOS-mode files
      // sneak in
      if (ch == '\r')
	{
	  ch = fgetc(in);
	}

      // check that the number of battlefields was correct and if so,
      // whether the id is non-empty
      if ((id_len == 0 && curr_bf > 0)
	  || (id_len > 0 && curr_bf != battlefields - 1))
	{
	  entry_destroy(&result);
	}
      else if (id_len == 0)
	{
	  // empty id and battlefields = 0 means end-of-input
	  free(result.distribution);
	  result.distribution = NULL;
	}
    }

  return result;
}

void entry_destroy(entry *e)
{
  if (e != NULL)
    {
      free(e->id);
      e->id = NULL;
      free(e->distribution);
      e->distribution = NULL;
    }
}